In an LTE (Long Term Evolution) system, a base station sends, to each UE (User Equipment), PDCCHs (Physical Downlink Control Channel) carrying various DCI (Downlink Control Information, uplink/downlink control information), and therefore, the UE needs to detect the PDCCHs, and acquire the various DCI carried by the PDCCHs. One PDCCH includes L consecutive CCEs (Control Channel Element) that are aggregated together. A search space is a set of PDCCHs to be detected by UE, and the search space includes two types: a CSS (Common Search Space) and a UESS (UE Specific Search Space). The CSS is a search space that multiple UEs in a cell need to listen on, and the UESS is a search space that a particular UE in a cell needs to listen on.
In an LTE TDD (Time Division Duplexing) system, a base station may dynamically configure a TDD uplink-downlink configuration, for example, change the uplink-downlink configuration at intervals of 10 ms to 40 ms. In this case, the base station needs to continually send, to UE, a PDCCH carrying uplink-downlink configuration information, where the PDCCH carrying uplink-downlink configuration information is located in the CSS. However, the CSS in an existing system has a limited size, and if multiple types of DCI need to be carried by PDCCHs in the CSS at a same moment, the base station may fail to find an idle PDCCH in the CSS to carry and send the uplink-downlink configuration information, and consequently, the UE cannot acquire current uplink-downlink configuration information, and the UE may fail to send and receive data normally.